The present invention relates to methods for adding fertilizer nutrients, particularly phosphorus, to agricultural irrigation systems, including particularly agricultural micro-irrigation and sprinkler systems.
The agriculture industry adds fertilizers to the plant environs, such as the soil, to enhance crop growth and subsequent yields. Commercial fertilizers are usually selected of a variety of formulations depending on the crop and its nutrient requirements.
Fertilizers generally are classified according to their NPK content. NPK is common terminology used in the fertilizer industry and stands for: (1) N—the amount of nitrogen in the formulation as N; (2) P—the amount of phosphorus in the formulation as P2O5; and (3) K—the amount of potassium in the formulation as K2O. Nitrogen, phosphorus and potassium are the basic plant nutrients or macronutrients that are taken up and utilized by the growing crops, and that are provided by the addition of fertilizers (NPK fertilizers).
A fertilizer, as that term is used herein and as generally understood, refers to the nutrient-containing materials used to deliver fertilizer nutrients to a crop. Conventional fertilizers typically will contain materials that are extraneous to the crop's nutrient-uptake (“nutrient-extraneous materials”) but which, for practical and/or other reasons, are necessary to the delivery of the nutrients. The process of delivering fertilizer nutrients to crops is referred to as fertilization.
The fertilization method of adding fertilizers to the water being used to irrigate the crops is called “fertigation”, reflecting this combination of irrigation and fertilization. Fertigation reduces the labor expended in the addition of fertilizers.
To conserve water, which is decreasing in availability and increasing in cost, current conventional technology includes micro-irrigation systems that deliver precise amounts of water directly to the soil holding the root system of the plant that is being grown. In the past twenty to thirty years, a large percentage of crop producers in the western and southwestern United States have converted from flood and sprinkler irrigation systems to micro-irrigation technology. Micro-irrigation systems contain devices called emitters, micro-sprinklers or other such devices that provide the precise amounts of water directly to the desired soil site, namely the soil holding the roots of the plant or crop being irrigated. Upon conversion to micro-irrigation systems, farmers began adding fertilizers through them.
Micro-irrigation systems, unfortunately, are sensitive to water quality and the inclusion of fertilizers and other additives. The sensitivity of micro-irrigation systems to water quality and additives stems from the refinement of the micro components in a micro-irrigation system. These emitters, micro-sprinklers or other micro devices deliver the desired precise amounts of water so long as they do not plug or foul. Plugging occurs when deposits, from any source, build up inside these devices. The smallest particle or foreign material can cause fouling of these devices because these devices have very tiny orifices and/or a long tortuous narrow passageway that provide the requisite pressure for delivery of precise amounts of water in a uniform manner to each plant in the crop being irrigated. Water quality and the inclusion of fertilizers can, and frequently does, cause severe plugging problems. The problems arise from a number of factors: (1) the irrigation water is typically obtained from wells, reservoirs, canals, lakes, or rivers which contain various amounts of dissolved minerals; and (2) fertilizers can form insoluble salts and/or cause particulate formation when added to the water. Macro-irrigation systems mainly tolerate these conditions, while micro-irrigation systems are extremely intolerant.
In more detail, the addition of fertilizer formulations to the micro-irrigation water increases the loading of inorganic salts over that already in the water. When the loading, or the combined loading, is too high, the solubilities of at least some of the naturally-occurring minerals and/or added compounds are exceeded and particulate formation increases dramatically. When particulates form, significant deposits begin to build up throughout the entire micro-irrigation system. The end result is plugging of the emitters or micro-sprinklers.
Plugging results in uneven distribution of water and nutrients to the crop being irrigated. In some cases, complete shut-down of the irrigation system occurs. Therefore problem-free use of additives such as fertilizers in micro-irrigation systems is normally seen only in irrigation systems that use relatively pure water sources.
The conventional agricultural practice is to make intermittent or periodic applications of fertilizers. Such intermittent additions might be a single addition, or a plurality of spaced-apart or set-apart additions, of large amounts (high concentrations) of fertilizer during a brief time interval each growing season or crop cycle. (The number of applications per growing season or crop cycle usually depends on the crop and/or the type of fertilizer being added.) When the fertilizer-delivery method is fertigation, fertilizers are typically slug fed into the irrigation system as quickly as possible to minimize the labor requirements and ease material handling. Slug feeding of a block (portion of a field) normally entails feeding the large amounts (high concentrations) of fertilizer to the irrigation water over a six to seven hour period during irrigation, and then, after the fertilizer feed is shut off, continuing the irrigation of that block for an additional two to three hours to rinse out all of the fertilizer that is contained inside the irrigation system, insuring that all of the fertilizer intended for the block is in fact delivered to the block. Fertigation reduces equipment, fuel and labor costs in comparison to mechanical delivery of fertilizers to the crop, and thus fertigation achieves a significant overall cost savings.
The cost of commercial fertilizer formulations is, however, itself significant, and commercially viable fertilizer formulations (formulations sufficiently inexpensive for bulk agricultural use) typically include, as mentioned above, nutrient-extraneous materials which do not contribute to plant nutrition, and can even be undesirable components.
The term “micro-irrigation” as used herein and in the claims refers to microsprinkers, drip, and subsurface drip systems.